Image sensor device

ABSTRACT

An image sensor device is provided. The image sensor device includes a substrate having a front surface, a back surface, and a light-sensing region. The image sensor device includes a first isolation structure extending from the front surface into the substrate. The first isolation structure includes a first insulating layer and an etch stop layer, the first insulating layer extends from the front surface into the substrate, the etch stop layer is between the first insulating layer and the substrate, and the etch stop layer, the first insulating layer, and the substrate are made of different materials. The image sensor device includes a second isolation structure extending from the back surface into the substrate. The second isolation structure is in direct contact with the etch stop layer, the second isolation structure surrounds the light-sensing region, and the second isolation structure includes a light-blocking structure.

CROSS REFERENCE

This application is a Divisional of U.S. application Ser. No.15/807,980, filed on Nov. 9, 2017, the entirety of which is incorporatedby reference herein.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experienced rapidgrowth. Technological advances in IC materials and design have producedgenerations of ICs where each generation has smaller and more complexcircuits than the previous generation. In the course of IC evolution,functional density (i.e., the number of interconnected devices per chiparea) has generally increased while geometric size (i.e., the smallestcomponent that can be created using a fabrication process) hasdecreased. Such advances have increased the complexity of processing andmanufacturing ICs. For these advances, similar developments in ICprocessing and manufacturing are needed.

Along with the advantages realized from reducing geometric size,improvements are being made directly to the IC devices. One such ICdevice is an image sensor device. An image sensor device includes apixel array (or grid) for detecting light and recording intensity(brightness) of the detected light. The pixel array responds to thelight by accumulating a charge. The higher the light intensity, thegreater the charge that is accumulated in the pixel array. Theaccumulated charge is then used (for example, by other circuitry) toprovide image information for use in a suitable application, such as adigital camera.

However, since the feature sizes continue to decrease, fabricationprocesses continue to become more difficult to perform. Therefore, it isa challenge to form reliable image sensor devices at smaller and smallersizes.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It shouldbe noted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1A-1E are cross-sectional views of various stages of a process forforming an image sensor device, in accordance with some embodiments.

FIG. 2A is a top view of the semiconductor substrate, the etch stoplayer, and the insulating layer of FIG. 1B, in accordance with someembodiments.

FIG. 2B is a top view of the light-blocking structure and the insulatinglayer of FIG. 1D, in accordance with some embodiments.

FIG. 3 is a cross-sectional view of an image sensor device, inaccordance with some embodiments.

FIG. 4 is a cross-sectional view of an image sensor device, inaccordance with some embodiments.

FIG. 5 is a cross-sectional view of an image sensor device, inaccordance with some embodiments.

FIG. 6 is a cross-sectional view of an image sensor device, inaccordance with some embodiments.

FIG. 7 is a cross-sectional view of an image sensor device, inaccordance with some embodiments.

FIG. 8 is a cross-sectional view of an image sensor device, inaccordance with some embodiments.

FIG. 9 is a cross-sectional view of an image sensor device, inaccordance with some embodiments.

FIG. 10 is a cross-sectional view of an image sensor device, inaccordance with some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly. It is understood thatadditional operations can be provided before, during, and after themethod, and some of the operations described can be replaced oreliminated for other embodiments of the method.

FIGS. 1A-1E are cross-sectional views of various stages of a process forforming an image sensor device 100, in accordance with some embodiments.As shown in FIG. 1A, a semiconductor substrate 110 is provided. Thesemiconductor substrate 110 has a front surface 112 and a back surface114 opposite to the front surface 112. The semiconductor substrate 110has a thickness T1, in accordance with some embodiments. The thicknessT1 is equal to a distance between the front surface 112 and the backsurface 114, in accordance with some embodiments.

The semiconductor substrate 110 may be a silicon substrate doped with aP-type dopant such as boron, in which case the semiconductor substrate110 is a P-type substrate. Alternatively, the semiconductor substrate110 could be another suitable semiconductor material. For example, thesemiconductor substrate 110 may be a silicon substrate doped with anN-type dopant such as phosphorous or arsenic, in which case thesubstrate is an N-type substrate. The semiconductor substrate 110 mayinclude other elementary semiconductor materials such as germanium.

As shown in FIG. 1A, a portion of the semiconductor substrate 110 isremoved to form a trench 116 in the semiconductor substrate 110, inaccordance with some embodiments. The trench 116 extends from the frontsurface 112 into the semiconductor substrate 110, in accordance withsome embodiments. The trench 116 surrounds the portions of thesemiconductor substrate 110, in accordance with some embodiments.

The trench 116 has a bottom surface 116 a and inner walls 116 b, inaccordance with some embodiments. The inner walls 116 b are connected to(or adjacent to) the bottom surface 116 a, in accordance with someembodiments. The trench 116 has a depth D1, in accordance with someembodiments. In some embodiments, a ratio of the depth D1 to thethickness T1 ranges from about 0.02 to about 0.5.

As shown in FIG. 1A, an etch stop layer 122 is formed over thesemiconductor substrate 110 to cover the bottom surface 116 a, the innerwalls 116 b, and the front surface 112, in accordance with someembodiments. The etch stop layer 122 covering the bottom surface 116 ahas a thickness T2, in accordance with some embodiments. The etch stoplayer 122 covering the inner walls 116 b has a thickness T3, inaccordance with some embodiments. The thickness T2 is greater than thethickness T3, in accordance with some embodiments.

The etch stop layer 122 is used to control a subsequent etch processperformed on the semiconductor substrate 110, in accordance with someembodiments. The etch stop layer 122 and the semiconductor substrate 110are made of different materials, in accordance with some embodiments.The etch stop layer 122 is made of an insulating material, in accordancewith some embodiments.

The etch stop layer 122 is made of silicon nitride, silicon oxynitride,silicon dioxide, silicon carbide, a combination thereof, or the like, inaccordance with some embodiments. The etch stop layer 122 is formedusing a deposition process, such as a chemical vapor deposition process,a physical vapor deposition process, an atomic layer deposition process,or another suitable deposition process.

As shown in FIG. 1A, an insulating layer 124 is formed over the etchstop layer 122, in accordance with some embodiments. The insulatinglayer 124 is filled in the trench 116, in accordance with someembodiments. The etch stop layer 122, the insulating layer 124, and thesemiconductor substrate 110 are made of different materials, inaccordance with some embodiments.

The insulating layer 124 is made of silicon dioxide, silicon nitride,silicon oxynitride, fluoride-doped silicate glass (FSG), a low-Kdielectric material, another suitable insulating material, orcombinations thereof. The insulating layer 124 is formed using adeposition process, such as a chemical vapor deposition process, aphysical vapor deposition process, or another suitable depositionprocess.

As shown in FIG. 1B, the insulating layer 124 and the etch stop layer122 outside of the trench 116 are removed, in accordance with someembodiments. After the removal process, the insulating layer 124 and theetch stop layer 122 remaining in the trench 116 together form anisolation structure 120, in accordance with some embodiments.

In some embodiments, the isolation structure 120 is used to definesubsequently formed light-sensing regions in the semiconductor substrate110, and to electrically isolate neighboring devices (e.g. transistors)from one another. In some embodiments, the isolation features 120 areformed adjacent to or near the front surface 112.

The removal process includes a planarization process, such as a chemicalmechanical polishing process, in accordance with some embodiments.Therefore, a top surface 122 a of the etch stop layer 122 and a topsurface 124 a of the insulating layer 124 are substantially coplanar (orsubstantially aligned with each other), in accordance with someembodiments. The term “substantially coplanar” in the application mayinclude small deviations from coplanar geometries. The deviations may bedue to manufacturing processes.

FIG. 2A is a top view of the semiconductor substrate 110, the etch stoplayer 122, and the insulating layer 124 of FIG. 1B, in accordance withsome embodiments. As shown in FIGS. 1B and 2A, light-sensing regions 118are formed in the portions of the semiconductor substrate 110 surroundedby the trench 116 (or the isolation structure 120), in accordance withsome embodiments. The light-sensing regions 118 are also referred to asradiation-sensing regions, in accordance with some embodiments.

The light-sensing regions 118 are formed using one or more ionimplantation processes or diffusion processes, in accordance with someembodiments. The light-sensing regions 118 are doped with a dopingpolarity opposite from that of the semiconductor substrate 110. Thelight-sensing regions 118 are formed close to (or adjacent to, or near)the front surface 112 of the semiconductor substrate 110.

The light-sensing regions 118 are operable to sense incident light (orincident radiation) that enters the light-sensing regions 118. Theincident light may be visible light. Alternatively, the incident lightmay be infrared (IR), ultraviolet (UV), X-ray, microwave, other suitabletypes of light, or a combination thereof.

Image sensing elements are formed over the light-sensing regions 118,and for the sake of simplicity, detailed structures of the image sensingelements are not shown in figures of the present disclosure, inaccordance with some embodiments. The image sensing elements includepinned layers, photodiode gates, reset transistors, source followertransistors, and transfer transistors, in accordance with someembodiments.

The transfer transistors are electrically connected with thelight-sensing regions 118 to collect (or pick up) electrons generated byincident light (incident radiation) traveling into the light-sensingregions 118 and to convert the electrons into voltage signals, inaccordance with some embodiments.

As shown in FIG. 1B, an interconnection structure 130 is formed over thefront surface 112, in accordance with some embodiments. Theinterconnection structure 130 includes a number of patterned dielectriclayers and conductive layers that couple to various doped features,circuitry, photodiode gates, reset transistors, source followertransistors, and transfer transistors. For example, the interconnectionstructure 130 includes an interlayer dielectric (ILD) layer 132 and amultilayer interconnection (MLI) structure 134 in the ILD layer 132.

The MLI structure 134 includes conductive lines 134 a and vias (orcontacts) 134 b connected between the conductive lines 134 a. It shouldbe understood that the conductive lines 134 a and the vias 134 b aremerely exemplary. The actual positioning and configuration of theconductive lines 134 a and the vias 134 b may vary depending on designneeds and manufacturing concerns.

Afterwards, a carrier substrate 140 is bonded with the interconnectionstructure 130, in accordance with some embodiments. The carriersubstrate 140 includes a silicon substrate, a glass substrate or anothersuitable substrate. Thereafter, as shown in FIGS. 1B and 1C, a thinningprocess is performed to thin the semiconductor substrate 110 from theback surface 114. The thinning process may include a chemical mechanicalpolishing process.

Afterwards, as shown in FIG. 1C, the semiconductor substrate 110 isflipped over, and a trench 119 is formed in the semiconductor substrate110, in accordance with some embodiments. The trench 119 extends fromthe back surface 114 into the semiconductor substrate 110, in accordancewith some embodiments. The trench 119 is between each two adjacentlight-sensing regions 118, in accordance with some embodiments. Thetrench 119 surrounds each of the light-sensing regions 118, inaccordance with some embodiments.

In some embodiments, the trench 119 is above the isolation structure120. In some embodiments, the trench 119 exposes the isolation structure120. The isolation structure 120 has a surface (or an end surface) 120 afacing the back surface 114, in accordance with some embodiments. Thetrench 119 exposes the surface 120 a, in accordance with someembodiments. The trench 119 exposes the etch stop layer 122, inaccordance with some embodiments.

The trench 119 has a depth D2, in accordance with some embodiments. Insome embodiments, a ratio of the depth D2 of the trench 119 to thethickness T1 of the semiconductor substrate 110 ranges from about 0.2 toabout 0.98. In some embodiments, the ratio of the depth D1 of the trench119 to the thickness T1 of the semiconductor substrate 110 ranges fromabout 0.5 to about 0.98. The depth D2 is greater than the depth D1, inaccordance with some embodiments.

Afterwards, as shown in FIG. 1D, an insulating layer 150 is formed overthe back surface 114 and in the trench 119, in accordance with someembodiments. The insulating layer 150 continuously and conformallycovers a bottom surface 119 a (i.e. the surface 120 a) and the innerwalls 119 b of the trench 119 and the back surface 114, in accordancewith some embodiments.

The insulating layer 150 is also referred to as a liner layer, inaccordance with some embodiments. The insulating layer 150 is in directcontact with the isolation structure 120 and the semiconductor substrate110, in accordance with some embodiments. The insulating layer 150 is indirect contact with the etch stop layer 122, in accordance with someembodiments.

In some embodiments, the insulating layer 150 is used to passivate theback surface 114, the bottom surface 119 a, and the inner walls 119 b.In some embodiments, the insulating layer 150 is also used toelectrically isolate the light-sensing regions 118 from one another toreduce electrical crosstalk between the light-sensing regions 118.

The insulating layer 150 includes silicon dioxide, in accordance withsome embodiments. The insulating layer 150 includes a high-k material, adielectric material, or other suitable insulating materials. The high-kmaterial may include hafnium oxide, tantalum pentoxide, zirconiumdioxide, aluminum oxide, other suitable materials, or a combinationthereof.

The dielectric material includes, for example, silicon nitride, siliconoxynitride, other suitable materials, or a combination thereof. Theinsulating layer 150 is formed by, for example, a thermal oxidationprocess or a deposition process, such as a chemical vapor depositionprocess or a physical vapor deposition process.

Thereafter, as shown in FIG. 1D, a light-blocking structure 160 isformed in the trench 119, in accordance with some embodiments. Thelight-blocking structure 160 is formed over the insulating layer 150, inaccordance with some embodiments. A top surface 150 a of the insulatinglayer 150 and a top surface 160 a of the light-blocking structure 160are substantially coplanar, in accordance with some embodiments.

FIG. 2B is a top view of the light-blocking structure 160 and theinsulating layer 150 of FIG. 1D, in accordance with some embodiments.FIG. 1D is a cross-sectional view illustrating an intermediate structureof an image sensor device along a sectional line I-I′ in FIG. 2B, inaccordance with some embodiments. As shown in FIGS. 1D and 2B, thetrench 119 and the light-blocking structure 160 therein surround each ofthe light-sensing regions 118, in accordance with some embodiments.

The insulating layer 150 is between the light-blocking structure 160 andthe semiconductor substrate 110 to separate the light-blocking structure160 from the semiconductor substrate 110, in accordance with someembodiments. The insulating layer 150 electrically insulates thelight-blocking structure 160 from the semiconductor substrate 110, inaccordance with some embodiments.

The trench 119 is filled with the insulating layer 150 and thelight-blocking structure 160, in accordance with some embodiments. Thelight-blocking structure 160 is between each two adjacent light-sensingregions 118, in accordance with some embodiments. The light-blockingstructure 160 is used to block incident light to prevent the incidentlight from traveling between different light-sensing regions 118, inaccordance with some embodiments.

In some embodiments, the light-blocking structure 160 includes a lightreflection structure. In some embodiments, the light reflectionstructure has a lower refractive index than that of the semiconductorsubstrate 110, and therefore a portion of the incident light arriving atthe light reflection structure is reflected, which is a phenomenoncalled “total internal reflection”. The light reflection structureincludes dielectric materials, such as silicon dioxides, siliconnitrides, or silicon carbides.

In some embodiments, the light reflection structure has a lightreflectivity ranging from about 60% to about 100%. In some embodiments,the light reflection structure includes a metal material or an alloymaterial. The light reflection structure includes Al, W, Cu, Ti, analloy thereof, a combination thereof, or another suitable reflectivematerial.

Alternatively, in some embodiments, the light-blocking structure 160includes a light absorption structure. In some embodiments, the lightabsorption structure has a light absorptivity ranging from about 60% toabout 100%. In some embodiments, the light absorption structure is usedto absorb the incident light arriving at the light absorption structureto prevent the incident light from traveling between differentlight-sensing regions 118.

In some embodiments, the light absorption structure includes a blacksilicon material, a semiconductor material with a band gap smaller than1.5 eV (e.g., Ge, InSb. or InAs), or a polymer material (e.g., an opaquepolymer material). In some embodiments, the light absorption structureincludes a non-visible light filter (e.g. an IR filter or a UV filter)enabled to block visible light and transmit non-visible light.

In some embodiments, the method of forming the light-blocking structure160 includes depositing a light-blocking material layer on thesemiconductor substrate 110 and filled in the trench 119; and removingthe light-blocking material layer outside of the trench 119.

The method of depositing the light-blocking material layer includesperforming a chemical vapor deposition (CVD) process, a physical vapordeposition (PVD) process, a coating process, or another suitableprocess. The method of removing the light-blocking material layeroutside of the trench 119 includes performing a chemical mechanicalpolishing (CMP) process or another suitable process.

The light-blocking structure 160 and the insulating layer 150 togetherform an isolation structure S, in accordance with some embodiments. Insome embodiments, the isolation structure S is used to separate thelight-sensing regions 118 from one another, and to electrically isolateneighboring devices (e.g. transistors) from one another.

The isolation structure S extends from the back surface 114 into thesemiconductor substrate 110, in accordance with some embodiments. Theisolation structure S surrounds each of the light-sensing regions 118,in accordance with some embodiments. The isolation structure S issubstantially aligned with the isolation structure 120, in accordancewith some embodiments.

The isolation structure S is in direct contact with the isolationstructure 120, in accordance with some embodiments. In some embodiments,there is no gap (or no semiconductor substrate 110) between end surfaces120 a and S1 of the isolation structures 120 and S. Therefore, theisolation structures 120 and S may reduce optical crosstalk andelectrical crosstalk between adjacent light-sensing regions 118.

Thereafter, as shown in FIG. 1E, an anti-reflection coating (ARC) layer170 and a buffer layer 180 are sequentially formed over the back surface114 of the semiconductor substrate 110, in accordance with someembodiments. The ARC layer 170 is used to reduce optical reflection fromthe back surface 114 of the semiconductor substrate 110 to ensure thatmost of an incident light enters the light-sensing regions 118 and issensed.

The ARC layer 170 may be made of a high-k material, a dielectricmaterial, other applicable materials, or a combination thereof. Thehigh-k material may include hafnium oxide, tantalum pentoxide, zirconiumdioxide, aluminum oxide, other suitable materials, or a combinationthereof. The dielectric material includes, for example, silicon nitride,silicon oxynitride, other suitable materials, or a combination thereof.

The buffer layer 180 is used as a buffer between the ARC layer 170 andsubsequently formed overlying layers. The buffer layer 180 may be madeof a dielectric material or other suitable materials. For example, thebuffer layer 180 is made of silicon dioxide, silicon nitride, siliconoxynitride, other applicable materials, or a combination thereof.

Thereafter, as shown in FIG. 1E, a reflective grid 190 is formed overthe buffer layer 180, in accordance with some embodiments. Thereflective grid 190 may include reflective elements 192. In someembodiments, the reflective elements 192 are aligned with thelight-blocking structure 160. That is, the reflective elements 192 areright over the light-blocking structure 160, in accordance with someembodiments. In some other embodiments, the reflective elements 192 arenot right over the light-blocking structure 160, in accordance with someembodiments. Each of the reflective elements 192 is used to prevent theincident light from entering a neighboring light-sensing region 118. Thecrosstalk problems between the light-sensing regions 118 are thusprevented or reduced.

In some embodiments, the reflective grid 190 is made of a reflectivematerial such as a metal material. The reflective grid 190 may be madeof aluminum, silver, copper, titanium, platinum, tungsten, tantalum,tantalum nitride, other suitable materials, or a combination thereof. Insome embodiments, the reflective grid 190 is formed over the bufferlayer 180 using a suitable process. The suitable process includes, forexample, a PVD process, an electroplating process, a CVD process, otherapplicable processes, or a combination thereof.

Afterwards, a dielectric layer 210 is formed over the buffer layer 180to cover the reflective grid 190, in accordance with some embodiments.The dielectric layer 210 may be made of silicon dioxide, siliconnitride, silicon oxynitride, or other suitable materials. The dielectriclayer 210 is formed by a CVD process or another suitable process. Thedielectric layer 210 has multiple recesses 212R, 212G, and 212B.

Thereafter, visible light filters (such as color filters 220R, 220G, and220B) are formed in the recesses 212R, 212G, and 212B, respectively. Insome embodiments, the visible light filters may be used to filterthrough visible light. The color filters 220R, 220G, and 220B may beused to filter through a red wavelength band, a green wavelength band,and a blue wavelength band, respectively. In some embodiments, thelight-blocking structure 160 includes a non-visible light filter (e.g.an IR filter or a UV filter) enabled to block the visible light passingthough the visible light filters.

Afterwards, lenses 230 are respectively formed over the color filters220R, 220G, and 220B, in accordance with some embodiments. The lenses230 are used to direct or focus the incident light. The lenses 230 mayinclude a microlens array. The lenses 230 may be made of a hightransmittance material. For example, the high transmittance materialincludes transparent polymer material (such as polymethylmethacrylate,PMMA), transparent ceramic material (such as glass), other applicablematerials, or a combination thereof. In this step, an image sensordevice 100 is substantially formed, in accordance with some embodiments.

As shown in FIG. 1E, an incident light L passing through the colorfilters 220R and arriving at the light-blocking structure 160 may beabsorbed or reflected by the light-blocking structure 160. Therefore,the light-blocking structure 160 may reduce optical crosstalk betweenadjacent light-sensing regions 118.

Furthermore, since the isolation structure 120 is in direct contact withthe isolation structure S, the isolation structures 120 and S togethercompletely separate the light-sensing regions 118 from one another, inaccordance with some embodiments. As a result, the isolation structures120 and S may further reduce optical crosstalk.

In the image sensor device 100, the isolation structure 120 extends fromthe front surface 112 into the semiconductor substrate 110, inaccordance with some embodiments. The isolation structure 120 surroundsthe light-sensing regions 118, in accordance with some embodiments.

The insulating layer 124 extends from the front surface 112 into thesemiconductor substrate 110, in accordance with some embodiments. Theetch stop layer 122 is positioned between the insulating layer 124 andthe isolation structure S, in accordance with some embodiments. Thelight-blocking structure 160 extends from the back surface 114 into thesemiconductor substrate 110, in accordance with some embodiments.

A minimum width W1 m of the isolation structure S in the trench 119 isless than a minimum width W2 m of the isolation structure 120, inaccordance with some embodiments. A width W1 of the isolation structureS in the trench 119 continuously decreases from the back surface 114 tothe isolation structure 120 thereunder, in accordance with someembodiments. The width W1 of the isolation structure S in the trench 119continuously decreases in a direction V1 toward the front surface 112,in accordance with some embodiments.

A width W2 of the isolation structure 120 continuously decreases fromthe front surface 112 to the isolation structure S thereabove, inaccordance with some embodiments. The width W2 of the isolationstructure 120 continuously decreases in a direction V2 toward the backsurface 114, in accordance with some embodiments.

FIG. 3 is a cross-sectional view of an image sensor device 300, inaccordance with some embodiments. As shown in FIG. 3, the image sensordevice 300 is similar to the image sensor device 100 of FIG. 1E, exceptthat the etch stop layer 122 of the image sensor device 300 covers onlya portion of the inner walls 116 b adjacent to the bottom surface 116 aof the trench 116, in accordance with some embodiments.

The etch stop layer 122 of the image sensor device 300 does not coverthe inner walls 116 b adjacent to the front surface 112, in accordancewith some embodiments. Therefore, the aspect ratio of the trench 116 maybe reduced, which may improve the yield of the process for filling theinsulating layer 124 into the trench 116.

FIG. 4 is a cross-sectional view of an image sensor device 400, inaccordance with some embodiments. As shown in FIG. 4, the image sensordevice 400 is similar to the image sensor device 100 of FIG. 1E, exceptthat the ratio of the depth D1 of the trench 116 to the thickness T1 ofthe semiconductor substrate 110 of the image sensor device 400 isgreater than that of the image sensor device 100, in accordance withsome embodiments. Therefore, the aspect ratio of the trench 119 isreduced.

As a result, the yield of the process for filling the light-blockingstructure 160 into the trench 119 is improved. The ratio of the depth D1of the trench 116 to the thickness T1 of the semiconductor substrate 110of the image sensor device 400 ranges from about 0.3 to about 0.5.

FIG. 5 is a cross-sectional view of an image sensor device 500, inaccordance with some embodiments. As shown in FIG. 5, the image sensordevice 500 is similar to the image sensor device 100 of FIG. 1E, exceptthat the isolation structure S extends into the isolation structure 120of the image sensor device 500, in accordance with some embodiments.

The trench 119 extends into the isolation structure 120, in accordancewith some embodiments. The isolation structure S in the trench 119 ispartially formed in the isolation structure 120, in accordance with someembodiments. The trench 119 extends into the etch stop layer 122, inaccordance with some embodiments. The trench 119 does not pass throughthe etch stop layer 122, in accordance with some embodiments. A portionof the etch stop layer 122 is between the insulating layer 124 and theisolation structure S to separate the insulating layer 124 from theisolation structure S, in accordance with some embodiments.

The isolation structure S has a first end portion E1 and a second endportion E2, in accordance with some embodiments. The first end portionE1 is between the second end portion E2 and the isolation structure 120,in accordance with some embodiments. The first end portion E1 partiallyextends into the isolation structure 120, in accordance with someembodiments. The first end portion E1 does not pass through the etchstop layer 122, in accordance with some embodiments.

There is a distance D3 between the bottom surface 116 a of the trench116 and the back surface 114, in accordance with some embodiments. Thedepth D2 of the trench 119 is greater than the distance D3, inaccordance with some embodiments. The sum of the depths D1 and D2 isgreater than the thickness T1 of the semiconductor substrate 110, inaccordance with some embodiments.

FIG. 6 is a cross-sectional view of an image sensor device 600, inaccordance with some embodiments. As shown in FIG. 6, the image sensordevice 600 is similar to the image sensor device 100 of FIG. 1E, exceptthat the minimum width W1 m of the isolation structure S in the trench119 is greater than the minimum width W2 m of the isolation structure120, in accordance with some embodiments. A maximum width W1 x of theisolation structure S in the trench 119 is greater than a maximum widthW2 x of the isolation structure 120, in accordance with someembodiments.

FIG. 7 is a cross-sectional view of an image sensor device 700, inaccordance with some embodiments. As shown in FIG. 7, the image sensordevice 700 is similar to the image sensor device 600 of FIG. 6, exceptthat the isolation structure 120 partially extends into the isolationstructure S, in accordance with some embodiments. The etch stop layer122 partially extends into the isolation structure S (or the insulatinglayer 150), in accordance with some embodiments.

There is a distance D3 between the bottom surface 116 a of the trench116 and the back surface 114, in accordance with some embodiments. Thedepth D2 of the trench 119 is greater than the distance D3, inaccordance with some embodiments. Before the formation of the isolationstructure S, the trench 119 exposes a surface 120 a and sidewalls 120 bof the isolation structure 120, in accordance with some embodiments.

The surface 120 a faces the back surface 114, and the sidewalls 120 bare adjacent to the surface 120 a, in accordance with some embodiments.The insulating layer 150 covers the surface 120 a and the sidewalls 120b of the isolation structure 120, in accordance with some embodiments.

FIG. 8 is a cross-sectional view of an image sensor device 800, inaccordance with some embodiments. As shown in FIG. 8, the image sensordevice 800 is similar to the image sensor device 100 of FIG. 1E, exceptthat the light-blocking structure 160 of the image sensor device 800includes a light reflection structure 162 and a light absorptionstructure 164, in accordance with some embodiments.

The light reflection structure 162 and the light absorption structure164 are sequentially formed in the trench 119, in accordance with someembodiments. The light absorption structure 164 is formed over the lightreflection structure 162, in accordance with some embodiments. The lightabsorption structure 164 has a top surface 164 a, in accordance withsome embodiments. The top surface 164 a and the top surface 150 a of theinsulating layer 150 are substantially coplanar, in accordance with someembodiments. The light absorption structure 164 and the light reflectionstructure 162 are made of different materials, in accordance with someembodiments.

In some embodiments, the light reflection structure 162 has a lowerrefractive index than that of the semiconductor substrate 110, andtherefore a portion of the incident light arriving at the lightreflection structure 162 is reflected. The light reflection structure162 includes dielectric materials, such as silicon dioxides, siliconnitrides, or silicon carbides.

In some embodiments, the light reflection structure 162 has a lightreflectivity ranging from about 60% to about 100%. In some embodiments,the light reflection structure 162 includes a metal material or an alloymaterial. The light reflection structure 162 includes Al, W, Cu, Ti, analloy thereof, a combination thereof, or another suitable reflectivematerial.

In some embodiments, the light absorption structure 164 has a lightabsorptivity ranging from about 60% to about 100%. In some embodiments,the light absorption structure 164 is used to absorb the incident lightarriving at the light absorption structure 164 to prevent the incidentlight from traveling between different light-sensing regions 118.

In some embodiments, the light absorption structure 164 includes a blacksilicon material, a semiconductor material with a band gap smaller than1.5 eV (e.g., Ge, InSb, or InAs), or a polymer material (e.g., an opaquepolymer material). In some embodiments, the light absorption structure164 includes a non-visible light filter (e.g. an IR filter or a UVfilter) enabled to block visible light and transmit non-visible light.

The light absorption structure 164 is positioned closer to the backsurface 114 than to the front surface 112, in accordance with someembodiments. The light reflection structure 162 is positioned betweenthe light absorption structure 164 and the isolation structure 120, inaccordance with some embodiments. A thickness T4 of the light absorptionstructure 164 is less than a thickness T5 of the light reflectionstructure 162, in accordance with some embodiments.

As shown in FIG. 8, an incident light L1 passing through the colorfilters 220R and arriving at the light reflection structure 162 isreflected by the light reflection structures 162, in accordance withsome embodiments. An incident light L2 passing through the color filters220R and arriving at the light absorption structure 164 may be absorbedby the light absorption structure 164, which prevents the incident lightL2 from being reflected to an adjacent light-sensing region 118.Therefore, the light-blocking structure 160 composed of the lightreflection structure 162 and the light absorption structure 164 mayreduce optical crosstalk.

FIG. 9 is a cross-sectional view of an image sensor device 900, inaccordance with some embodiments. As shown in FIG. 9, the image sensordevice 900 is similar to the image sensor device 100 of FIG. 1E, exceptthat the image sensor device 900 does not have the insulating layer 150of the image sensor device 100 of FIG. 1E, in accordance with someembodiments. The light-blocking structure 160 is made of an insulatingmaterial, in accordance with some embodiments.

The light-blocking structure 160 is in direct contact with the isolationstructure 120, in accordance with some embodiments. The light-blockingstructure 160 is in direct contact with the etch stop layer 122, inaccordance with some embodiments.

FIG. 10 is a cross-sectional view of an image sensor device, inaccordance with some embodiments. As shown in FIG. 10, the image sensordevice 1000 is similar to the image sensor device 900 of FIG. 9, exceptthat the image sensor device 1000 does not have the etch stop layer 122of the image sensor device 900 of FIG. 9, in accordance with someembodiments. The light-blocking structure 160 is in direct contact withthe insulating layer 124, in accordance with some embodiments.

In accordance with some embodiments, image sensor devices and methodsfor forming the same are provided. The methods (for forming the imagesensor devices) form a first isolation structure and a second isolationstructure in a semiconductor substrate and between adjacentlight-sensing regions of the semiconductor substrate. The semiconductorsubstrate has a front surface and a back surface. The first isolationstructure and the second isolation structure respectively extend fromthe front surface and the back surface and meet each other in thesemiconductor substrate. The light-sensing regions are completelyseparated from each other by the first isolation structure and thesecond isolation structure. Therefore, the first isolation structure andthe second isolation structure may block incident light arriving at thefirst isolation structure and the second isolation structure to preventthe incident light from traveling between adjacent light-sensingregions. Therefore, optical crosstalk between the light-sensing regionsis reduced. The first isolation structure and the second isolationstructure may electrically isolate the light-sensing regions from oneanother to reduce electrical crosstalk between the light-sensingregions.

In accordance with some embodiments, an image sensor device is provided.The image sensor device includes a substrate having a front surface, aback surface, and a light-sensing region. The image sensor deviceincludes a first isolation structure extending from the front surfaceinto the substrate. The first isolation structure surrounds thelight-sensing region, the first isolation structure includes a firstinsulating layer and an etch stop layer, the first insulating layerextends from the front surface into the substrate, the etch stop layeris between the first insulating layer and the substrate, and the etchstop layer, the first insulating layer, and the substrate are made ofdifferent materials. The image sensor device includes a second isolationstructure extending from the back surface into the substrate. The secondisolation structure is in direct contact with the etch stop layer, thesecond isolation structure surrounds the light-sensing region, and thesecond isolation structure includes a light-blocking structure.

In accordance with some embodiments, an image sensor device is provided.The image sensor device includes a substrate having a front surface, aback surface, and a light-sensing region. The image sensor deviceincludes a first isolation structure extending from the front surfaceinto the substrate. The first isolation structure surrounds thelight-sensing region. The image sensor device includes a secondisolation structure extending from the back surface into the substrateand the first isolation structure. The second isolation structuresurrounds the light-sensing region, the second isolation structure has afirst end portion in the first isolation structure, the first endportion has an end surface and a sidewall adjacent to the end surface,the first isolation structure covers the end surface and the sidewall,and the second isolation structure includes a light-blocking structure.

In accordance with some embodiments, an image sensor device is provided.The image sensor device includes a substrate having a front surface, aback surface, and a light-sensing region. The image sensor deviceincludes a first isolation structure extending from the front surfaceinto the substrate. The first isolation structure surrounds thelight-sensing region. The image sensor device includes a secondisolation structure extending from the back surface into the substrate.The second isolation structure surrounds the light-sensing region, thefirst isolation structure is partially embedded in the second isolationstructure, and the second isolation structure includes a light-blockingstructure.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. An image sensor device, comprising: a substratehaving a front surface, a back surface, and a light-sensing region; afirst isolation structure extending from the front surface into thesubstrate, wherein the first isolation structure surrounds thelight-sensing region, the first isolation structure comprises a firstinsulating layer and an etch stop layer, the first insulating layerextends from the front surface into the substrate, the etch stop layeris between the first insulating layer and the substrate, and the etchstop layer, the first insulating layer, and the substrate are made ofdifferent materials; and a second isolation structure extending from theback surface into the substrate, wherein the second isolation structureis in direct contact with the etch stop layer, the second isolationstructure surrounds the light-sensing region, and the second isolationstructure comprises a light-blocking structure.
 2. The image sensordevice as claimed in claim 1, wherein the light-blocking structureextends from the back surface into the substrate, and the secondisolation structure further comprises: a second insulating layer betweenthe light-blocking structure and the substrate and between thelight-blocking structure and the etch stop layer.
 3. The image sensordevice as claimed in claim 2, wherein the second insulating layer is indirect contact with the etch stop layer.
 4. The image sensor device asclaimed in claim 2, wherein the second insulating layer is partially inthe first isolation structure.
 5. The image sensor device as claimed inclaim 4, wherein the second insulating layer is partially in the etchstop layer.
 6. The image sensor device as claimed in claim 5, whereinthe etch stop layer is between the first insulating layer and the secondinsulating layer.
 7. The image sensor device as claimed in claim 2,wherein the etch stop layer is in direct contact with the firstinsulating layer, the second insulating layer, and the substrate.
 8. Theimage sensor device as claimed in claim 1, wherein the light-blockingstructure is partially in the first isolation structure.
 9. The imagesensor device as claimed in claim 1, wherein the first insulating layerhas an end surface and a sidewall adjacent to the end surface, the endsurface faces the second isolation structure, and the etch stop layercontinuously covers the end surface and the sidewall.
 10. The imagesensor device as claimed in claim 1, wherein the light blockingstructure comprises a light reflection structure with a first refractiveindex lower than a second refractive index of the substrate.
 11. Animage sensor device, comprising: a substrate having a front surface, aback surface, and a light-sensing region; a first isolation structureextending from the front surface into the substrate, wherein the firstisolation structure surrounds the light-sensing region; and a secondisolation structure extending from the back surface into the substrateand the first isolation structure, wherein the second isolationstructure surrounds the light-sensing region, the second isolationstructure has a first end portion in the first isolation structure, thefirst end portion has an end surface and a sidewall adjacent to the endsurface, the first isolation structure covers the end surface and thesidewall, and the second isolation structure comprises a light-blockingstructure.
 12. The image sensor device as claimed in claim 11, whereinthe first isolation structure comprises an insulating layer and an etchstop layer, the insulating layer extends from the front surface into thesubstrate, the etch stop layer wraps around the insulating layer, theetch stop layer covers the end surface and the sidewall, and the etchstop layer, the insulating layer, and the substrate are made ofdifferent materials.
 13. The image sensor device as claimed in claim 11,wherein the first isolation structure has a second end portion, thefirst end portion is embedded in the second end portion, and the secondend portion is wider than the first end portion.
 14. The image sensordevice as claimed in claim 11, wherein the light blocking structurecomprises a light reflection structure, and the light reflectionstructure is made of a metal material or an alloy material.
 15. Theimage sensor device as claimed in claim 11, wherein the light blockingstructure comprises a light absorption structure with a lightabsorptivity ranging from about 60% to about 100%.
 16. An image sensordevice, comprising: a substrate having a front surface, a back surface,and a light-sensing region; a first isolation structure extending fromthe front surface into the substrate, wherein the first isolationstructure surrounds the light-sensing region; and a second isolationstructure extending from the back surface into the substrate, whereinthe second isolation structure surrounds the light-sensing region, thefirst isolation structure is partially embedded in the second isolationstructure, and the second isolation structure comprises a light-blockingstructure.
 17. The image sensor device as claimed in claim 16, whereinthe first isolation structure comprises a first insulating layer and anetch stop layer, the first insulating layer extends from the frontsurface into the substrate, the etch stop layer wraps around the firstinsulating layer, and the etch stop layer is partially embedded in thesecond isolation structure.
 18. The image sensor device as claimed inclaim 17, wherein the light-blocking structure extends from the backsurface into the substrate, and the second isolation structure furthercomprises: a second insulating layer between the light-blockingstructure and the substrate and between the light-blocking structure andthe etch stop layer.
 19. The image sensor device as claimed in claim 18,wherein the etch stop layer is partially embedded in the secondinsulating layer.
 20. The image sensor device as claimed in claim 16,wherein a first end portion of the first isolation structure ispartially embedded in a second end portion of the second isolationstructure, and the second end portion is wider than the first endportion.